The relatively low power losses associated with distribution of power through harnessing of electricity has enabled the transmission of electric power over large distances. The relative efficiency of large stationary power plants often result in great distances between major sources of electric power input and electric power use/output. The electric power transmission lines between such power generation sources and power users is typically regulated by a public utility which maintains this power supply system, also referred to as “the grid.”
For the grid to function properly and supply electric power users with the power that they expect it is important that power input into the grid be at least as great as the demand for power outputted from the grid. Furthermore, it is important that voltage at various different locations within the grid be maintained and that the frequency of AC electric current within the grid also be properly maintained. An inefficient way to maintain the grid is to always have an excessive oversupply of electric power into the grid and merely discharge to ground the power that is not needed, so that users always have an abundant supply of electric power. However, such an approach is not optimal due to the significant waste of electric power involved, and the waste of resources utilized in generating such excess power. Rather it is beneficial that the grid maintain only a small margin between power generated and power used, and then that the grid be able to respond quickly to support function of the grid should supply drop unexpectedly (such as when a power plant has a failure event) or if demand increases abruptly (such as when demand is peaking for air conditioning in highly populated areas on a hot afternoon).
Less desirable solutions to this problem include having customers agree in advance to have their power interrupted should the supply and demand within the grid require “load shedding.” As another option, “rolling blackouts” or “rolling brownouts” can be resorted to where different portions of the grid are shut down sequentially or allowed to drop below desired minimum voltage or otherwise partially fail to fully meet demand.
To avoid these less desirable solutions to the problem of mismatch between electric demand and electric supply, it is also known to provide dispatchable distributed energy resources. Such distributed energy resources can be equipment which supplies power to the grid or equipment which draws power from the grid. Such distributed energy resources benefit from being dispatchable in that control over the operation of the unit is at least partially surrendered to the electric utility operator. The electric utility operator can then “dispatch” the distributed energy resource when needed to provide another tool for the grid operator in adequately supporting operation of the grid.
Various problems with dispatchable distributed energy resources warrant further innovation and improvement. It can be difficult to quantify the effect that dispatching a particular distributed energy unit will have on the grid. In some instances the distributed energy resource may have a theoretical expected effect on the grid when dispatched, but the actual effect of dispatching the distributed energy resource might vary significantly from the expected effect. Thus, an electric utility relying on theoretical or predicted load shedding benefits from dispatching particular distributed energy resources might dispatch a series of such distributed energy resources and not receive the expected benefit, leaving the grid in a vulnerable operational state. Accordingly, a need exists for more comprehensive evaluation of the impacts of dispatching particular distributed energy units and resources in advance, so that the utility can rely more completely on the load shedding results and other grid support benefits to be provided by dispatching a particular distributed energy resource.
Another problem with dispatchable distributed energy resources is that the quantity of load shedding provided by distributed energy resource can vary over time. In many instances, when a distributed energy resource is first dispatched only a small amount of load shedding is provided. This amount of load shedding will increase over some time interval until the distributed energy resource is providing the full load shedding benefit to the grid. However, during this time lag, while the distributed energy resource is passing through a transient mode of operation, the full anticipated load shedding benefit is not received. In many instances a grid operator needs to be able to rely on a fast and predictable response to a situation, such as a large power plant going offline unexpectedly. If dispatchable distributed energy resources are slow responding, the grid is left in a vulnerable state during this transient period. Also, predictable load shedding allows the grid to support ancillary services, even in non-emergency situations, such as to support the continuous flow of electricity so that supply will continually meet demand.
Dispatchable distributed energy resources come in a variety of different types and styles, some of which are significantly more expensive than others. From an economic standpoint, it is desirable to first dispatch low cost distributed energy resources to optimize financial performance along with adequate grid performance. With the particular needs for improvement to dispatchable distributed energy resources as described above, this invention is presented to more effectively support electric utility performance with dispatchable distributed energy resources of various types and through more effective and permanent monitoring and validation of the load shedding characteristics and benefits of different distributed energy resources in real-world conditions.